ABSTRACTThe anhydrous salts morpholinium (tetra-hydro-2-H-1,4-oxazin-4-ium) phen-oxy-acetate, C4H10NO(+)·C8H7O3 (-), (I), morpholinium (4-fluoro-phen-oxy)acetate, C4H10NO(+)·C8H6 FO3 (-), (II), and isomeric morpholinium (3,5-di-chloro-phen-oxy)acetate (3,5-D), (III), and morpholinium (2,4-di-chloro-phen-oxy)acetic acid (2,4-D), C4H10NO(+)·C8H5Cl2O3 (-), (IV), have been determined and their hydrogen-bonded structures are described. In the crystals of (I), (III) and (IV), one of the the aminium H atoms is involved in a three-centre asymmetric cation-anion N-H⋯O,O' R 1 (2)(4) hydrogen-bonding inter-action with the two carboxyl O-atom acceptors of the anion. With the structure of (II), the primary N-H⋯O inter-action is linear. In the structures of (I), (II) and (III), the second N-H⋯Ocarbox-yl hydrogen bond generates one-dimensional chain structures extending in all cases along [100]. With (IV), the ion pairs are linked though inversion-related N-H⋯O hydrogen bonds [graph set R 4 (2)(8)], giving a cyclic hetero-tetra-meric structure.

fig3: The atom-numbering scheme and the mol­ecular conformation of the morpholinium cation (B) and the 3,5-D anion (A) in (III), with displacement ellipsoids drawn at the 40% probability level. The cation–anion hydrogen bonds are shown as dashed lines.

Mentions:
The asymmetric units of (I)–(IV) comprise a morpholinium cation (B) and a phen­oxy­acetate anion (A) in (I) (Fig. 1 ▸), a (4-fluoro­phen­oxy)acetate anion (A) in (II) (Fig. 2 ▸), a 3,5-di­chloro­phen­oxy­acetate anion (A) in (III) (Fig. 3 ▸) and a (2,4-di­chloro­phen­oxy)acetate anion (A) in (IV) (Fig. 4 ▸). The conformation of the oxo­acetate side chains in the anions of (I) and (II) are essentially planar, with the defining torsion angle C1A—O11A—C12A—C13A = 176.75 (14) and 176.53 (14)°, respectively. This anti­periplanar (180±30°) conformation is similar to those of the parent acids PAA (−175.1°; Kennard et al., 1982 ▸), PFPA [176.0 (6)°; Smith et al., 1992 ▸] and their proton-transfer salts, e.g. the ammonium salts of PAA [−177.48 (18)°] and PFPA [−178.98 (17)°] (Smith, 2014 ▸). However, with the 3,5-D and 2,4-D salts, the side-chain conformations are both synclinal (90±30°) [−76.5 (2)° in (III) and 72.91 (19)° in (IV)], similar to that in the parent acid 2,4-D (75.2°; Smith et al., 1976 ▸), in the tryptaminium salt of 2,4-D [81.2 (6)°; Smith & Lynch, 2015a ▸] and in the 2:1 salt-adduct of 3,5-D with 4,4′-bi­pyridine [−71.6 (3)°; Lynch et al., 2003 ▸]. However, in the tryptaminium salt of 3,5-D (Smith & Lynch, 2015b ▸), the ammonium salts of both 2,4-D (Liu et al., 2009 ▸) and 3,5-D (Smith, 2014 ▸), the anti­periplanar conformation is found [equivalent torsion angles = −166.5 (3), 172.61 (8) and −171.35 (15)°, respectively].

fig3: The atom-numbering scheme and the mol­ecular conformation of the morpholinium cation (B) and the 3,5-D anion (A) in (III), with displacement ellipsoids drawn at the 40% probability level. The cation–anion hydrogen bonds are shown as dashed lines.

Mentions:
The asymmetric units of (I)–(IV) comprise a morpholinium cation (B) and a phen­oxy­acetate anion (A) in (I) (Fig. 1 ▸), a (4-fluoro­phen­oxy)acetate anion (A) in (II) (Fig. 2 ▸), a 3,5-di­chloro­phen­oxy­acetate anion (A) in (III) (Fig. 3 ▸) and a (2,4-di­chloro­phen­oxy)acetate anion (A) in (IV) (Fig. 4 ▸). The conformation of the oxo­acetate side chains in the anions of (I) and (II) are essentially planar, with the defining torsion angle C1A—O11A—C12A—C13A = 176.75 (14) and 176.53 (14)°, respectively. This anti­periplanar (180±30°) conformation is similar to those of the parent acids PAA (−175.1°; Kennard et al., 1982 ▸), PFPA [176.0 (6)°; Smith et al., 1992 ▸] and their proton-transfer salts, e.g. the ammonium salts of PAA [−177.48 (18)°] and PFPA [−178.98 (17)°] (Smith, 2014 ▸). However, with the 3,5-D and 2,4-D salts, the side-chain conformations are both synclinal (90±30°) [−76.5 (2)° in (III) and 72.91 (19)° in (IV)], similar to that in the parent acid 2,4-D (75.2°; Smith et al., 1976 ▸), in the tryptaminium salt of 2,4-D [81.2 (6)°; Smith & Lynch, 2015a ▸] and in the 2:1 salt-adduct of 3,5-D with 4,4′-bi­pyridine [−71.6 (3)°; Lynch et al., 2003 ▸]. However, in the tryptaminium salt of 3,5-D (Smith & Lynch, 2015b ▸), the ammonium salts of both 2,4-D (Liu et al., 2009 ▸) and 3,5-D (Smith, 2014 ▸), the anti­periplanar conformation is found [equivalent torsion angles = −166.5 (3), 172.61 (8) and −171.35 (15)°, respectively].

ABSTRACTThe anhydrous salts morpholinium (tetra-hydro-2-H-1,4-oxazin-4-ium) phen-oxy-acetate, C4H10NO(+)·C8H7O3 (-), (I), morpholinium (4-fluoro-phen-oxy)acetate, C4H10NO(+)·C8H6 FO3 (-), (II), and isomeric morpholinium (3,5-di-chloro-phen-oxy)acetate (3,5-D), (III), and morpholinium (2,4-di-chloro-phen-oxy)acetic acid (2,4-D), C4H10NO(+)·C8H5Cl2O3 (-), (IV), have been determined and their hydrogen-bonded structures are described. In the crystals of (I), (III) and (IV), one of the the aminium H atoms is involved in a three-centre asymmetric cation-anion N-H⋯O,O' R 1 (2)(4) hydrogen-bonding inter-action with the two carboxyl O-atom acceptors of the anion. With the structure of (II), the primary N-H⋯O inter-action is linear. In the structures of (I), (II) and (III), the second N-H⋯Ocarbox-yl hydrogen bond generates one-dimensional chain structures extending in all cases along [100]. With (IV), the ion pairs are linked though inversion-related N-H⋯O hydrogen bonds [graph set R 4 (2)(8)], giving a cyclic hetero-tetra-meric structure.